A method of measuring an azimuth angle of a target to be detected (object to be detected) by using a radar apparatus includes several systems. Typical systems include, for example, a scanning system disclosed, for example, in JP-A No. 2004-132734 and a mono-pulse system disclosed, for example, in JP-A No. 2004-239744.
The principle of the scanning system disclosed in JP-A No.2004-132734 is to be described with reference to FIG. 14.
FIG. 14 shows an example of a radar antenna 300 and a radiation beam pattern 302 generated by the antenna. As shown in the drawing, the beam pattern is restricted finely by combining antenna elements in plurality in the lateral direction and the radiation beam is deflected right and left. In the radar, the intensity of electric waves when emitted electric waves are returned by reflection at a target is measured, and it can be seen that the target is present in the direction of the azimuth angle with strong reception intensity.
Then, JP-A No.2004-239744 discloses a radar structure of a mono-pulse system, that is, having an antenna including one transmission antenna and two reception antenna (left) and reception antenna (right) disposed being opposed to each other, that is, at positions right and left to each other.
On the other hand, JP-A No.2005-43375 discloses an automobile periphery monitoring device capable of efficiently tracking an object even when the number of detection points increases by widening of the angle and increasing of the sensitivity. That is, the automobile periphery monitor device of JP-A No.2005-43375 includes an object position estimation device for estimating a position to be detected at present based on an object position data in the past for each of the objects detected in the past, a window setting device of providing a predetermined window around the estimation position of the object, and an object tracking device of determining object position data at present by using detection point data contained in the window and calculating a relative velocity of the object by using object position data detected in the past.
Further, JP-A No. H05-180933 discloses a method of estimating the position of a target obstacle in an automobile improved for the position estimation accuracy of a target obstacle. That is, the position estimation method of JP-A No. H05-180933 labels each obstacle data so as to affix an identical label to obstacle data close to each other on an ordinate, calculates the moving direction and the moving amount on every label based on data in the last time and the data at present, divides the moving amount by a sampling time to calculate a relative velocity on every label relative to one's own automobile, and estimates the position of the target obstacle after a predetermined time based on a relative velocity vector which is determined by the relative velocity and the moving direction.